Experiments will be continued in an effort to determine the mechanism of activation of latent fatty acid synthethase (FAS) in livers of starved or newly-hatched chicks in response to feeding. Latent enzyme is defined as enzyme activity which is not measured in vitro under optimum assay conditions but which can be measured after in vivo activation (in response to feeding) or after suitable in vitro manipulations which result in apparent activation of inactive enzyme. Attempts will be made to isolate the factors from cytosol of fed chicks responsible for activation of latent FAS. Studies will also be conducted in an effort to determine whether FAS rather than acetyl-CoA carboxylase becomes the rate-limiting enzyme for lipogenesis during various nutritional states. BIBLIOGRAPHIC REFERENCES: Donaldson, W.E. (1975) Glucose stimulation of fatty acid synthetase and acetyl-CoA carboxylase in liver of newly hatched chicks (Gallus domesticus). Comp. Biochem. Physiol. 50B: 391-394. Thayer, R.H. and W.E. Donaldson (1975) Mercury inhibition of fatty acid synthesis in chicks. Chem.-Biol. Interactions 11: 235-243.